Researcher Evaluates Bit, Rein Interaction with Equine Mouth

Having a better understanding about the mechanics of riders' hands' interactions with the horse's head can improve your horse's performance, comfort, and well-being, noted one researcher at a recent equitation science conference. Hilary M. Clayton, BVMS, PhD, Dipl. ACVSMR, MRCVS, Mary Anne McPhail Dressage Chair in Equine Sports Medicine at Michigan State University, explained that bits, nosebands, and headpieces all exert pressure on horses when we place pressure on the reins, which can vary considerably.

But new biomechanical findings in equitation science can help riders make more informed decisions about equipment use and also dispel certain myths about bridles, bits, and reins.

According to Clayton, soft tissues such as the tongue, for example, are better suited to handling pressure than hard tissues like the nose bone and the palate (the roof of the horse's mouth). "The horse's tongue can be very sensitive but it can also withstand a lot of different kinds of pressure," she said during her plenary lecture at the 2011 International Society for Equitation Science Conference, held Oct. 26-29 in Hooge Mierde, The Netherlands.

"From my point of view, I would be a lot more concerned about pressure directly on the hard tissues (and) the bones, rather than the soft tissues which have a lot more ability to absorb the forces," she said.

Using radiographs (X rays) and fluoroscopy (real-time radiography) of a horse's head while wearing a bridle and bit, Clayton evaluated the position of the bit in a horse's mouth with and without tension applied to the reins.

Using radiographs (X rays) and fluoroscopy (real-time radiography) of a horse's head while wearing a bridle and bit, Clayton evaluated the position of the bit in a horse's mouth with and without tension applied to the reins. When the bit was the appropriate size for the horse and adjusted correctly, she said, the tongue could slide up and down under the mouth piece.

"Relaxation of the tongue allowed the bit to sink into the tongue when tension was applied to the reins," Clayton said. "But if the center joint of a single-jointed bit (like a basic snaffle) poked forward into the hard palate, this appeared to be uncomfortable for the horse." This so-called "nutcracker action" could cause the horse to react by leaning into the bit or opening his mouth, Clayton continued.

"I think that some of the resistances that we see in different bits are actually the horse's way of trying to relieve pressure on the palate," she said.Essentially Clayton suggested that riders should try to avoid putting pressure on the hard tissues (like the palate and the jaw bones) and keep the pressure primarily on the tongue.

Early studies on one type of bitless bridle, on the other hand, showed that the pressure on the nose, under the chin, and on the poll is quite high, Clayton added. Although this research is still in its early stages, Clayton said she isn't convinced the bitless bridle is more humane.

"Some people are under the impression that if you take the bit out of the horse's mouth, then you solve a lot of problems--that the bit is a source of pain," she said. "I would caution you that taking the bit away and simply putting pressure on the horse's nose may not be a cure-all."

Even so, the bitless bridle might be a "useful alternative" for horses that are unable to wear a bit, such as those with a lacerated tongue, she said.

Clayton added that her parallel research on head and neck problems in riding horses underscores the need for bridles and bits that help riders ease horses into lightness and rounded positions and better support the rider's weight. "Our research on neck lesions shows that neck injuries are very common in riding horses," Clayton told The Horse.

In order to maintain a neck position required of a discipline, horses must "activate the deep stabilizing musculature of the neck to stabilize the individual intervertebral joints and avoid micro-motion that predisposes to arthritic changes," she said. "Core training exercises that focus on moving the neck through a wide range of motion in a variety of directions are the best way to activate and strengthen the deep cervical stabilizing musculature so that the horse can safely perform in different head and neck positions."

As riders recognize that each horse is different and will have different reactions to different kinds of tack, they will be able to better ensure their horses' well-being over both the short-term and the long-term, she said.

About the Author

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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